RF signals conducted by rectangular waveguides propagating in transverse electric propagation mode are converted to transverse electromagnetic mode at a transition between the waveguide and a microstrip conductor. Insertion loss, return loss and impedance matching are important factors of waveguide to microstrip transition performance. Another factor is bandwidth, which is related to the impedance match at the transition.
Waveguide to microstrip transitions incorporated, for example, in the feed assembly of a reflector antenna are subject to space and orientation constraints applied to minimize the overall dimensions of the feed assembly. Further, transition layout conflicts may arise between space requirements of transitions from adjacent feed waveguides of a multiple narrow beam feed assembly.
Prior waveguide to microstrip transitions have included waveguide tapering structures designed to concentrate the RF signal in the waveguide upon a microstrip inserted in-line within the waveguide end. However, these structures require a significant longitudinal dimension that may conflict with adjacent circuit structures and or result in an assembly that is unacceptably deep. Alternatively, traces upon a PCB have been inserted into a waveguide, normal to the waveguide but this also constrains the orientation of the PCB or requires a further angular transition to yet another PCB.
The increasing competition for mass market consumer reflector antennas and thereby for the subcomponents thereof such as feed assemblies has focused attention on cost reductions resulting from increased materials, manufacturing and service efficiencies. Further, reductions in required assembly operations and the total number of discrete parts are desired.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.